500 ml (18 fl oz) vegetable stock
3 tablespoons olive oil
1 onion, chopped
250 g (9 oz) cucumbers, chopped
250 g (9 oz) potatoes, diced
25 g (1 oz) lettuce, chopped
6 fresh mint leaves, plus extra to garnish
50 ml (2 fl oz) double cream
salt and pepper
Pour the stock into a pan and bring to the boil. Heat the oil in another pan, add the onion and cook over low heat, stirring occasionally, for 5 minutes, until softened.
Add the cucumber, potatoes, lettuce and mint, and cook for a further 5 minutes.
Season with salt and pepper to taste, pour in the hot stock and cook for about 15 minutes.
Transfer to a food processor and process to a purée. Pour into a pan and reheat.
Stir in the cream and heat for 5 minutes more.
Remove from the heat, leave to cool to room temperature, then chill in the refrigerator for several hours.
To serve, pour into a soup tureen and garnish with mint leaves.
15 min, plus 2 hours chilling